ref: b09398e98563c23b6988e77b7b5ab84c0e03ceb7
dir: /examples/bq.scm/
(define (bq-process2 x d) (define (splice-form? x) (or (and (pair? x) (or (eq? (car x) 'unquote-splicing) (eq? (car x) 'unquote-nsplicing) (and (eq? (car x) 'unquote) (length> x 2)))) (eq? x 'unquote))) ;; bracket without splicing (define (bq-bracket1 x) (if (and (pair? x) (eq? (car x) 'unquote)) (if (= d 0) (cadr x) (list cons ''unquote (bq-process2 (cdr x) (- d 1)))) (bq-process2 x d))) (define (bq-bracket x) (cond ((atom? x) (list list (bq-process2 x d))) ((eq? (car x) 'unquote) (if (= d 0) (cons list (cdr x)) (list list (list cons ''unquote (bq-process2 (cdr x) (- d 1)))))) ((eq? (car x) 'unquote-splicing) (if (= d 0) (list 'copy-list (cadr x)) (list list (list list ''unquote-splicing (bq-process2 (cadr x) (- d 1)))))) ((eq? (car x) 'unquote-nsplicing) (if (= d 0) (cadr x) (list list (list list ''unquote-nsplicing (bq-process2 (cadr x) (- d 1)))))) (else (list list (bq-process2 x d))))) (cond ((symbol? x) (list 'quote x)) ((vector? x) (let ((body (bq-process2 (vector->list x) d))) (if (eq? (car body) list) (cons vector (cdr body)) (list apply vector body)))) ((atom? x) x) ((eq? (car x) 'quasiquote) (list list ''quasiquote (bq-process2 (cadr x) (+ d 1)))) ((eq? (car x) 'unquote) (if (and (= d 0) (length= x 2)) (cadr x) (list cons ''unquote (bq-process2 (cdr x) (- d 1))))) ((or (> d 0) (not (any splice-form? x))) (let ((lc (lastcdr x)) (forms (map bq-bracket1 x))) (if (null? lc) (cons list forms) (if (null? (cdr forms)) (list cons (car forms) (bq-process2 lc d)) (nconc (cons list* forms) (list (bq-process2 lc d))))))) (else (let loop ((p x) (q ())) (cond ((null? p) ;; proper list (cons 'nconc (reverse! q))) ((pair? p) (cond ((eq? (car p) 'unquote) ;; (... . ,x) (cons 'nconc (nreconc q (if (= d 0) (cdr p) (list (list list ''unquote) (bq-process2 (cdr p) (- d 1))))))) (else (loop (cdr p) (cons (bq-bracket (car p)) q))))) (else ;; (... . x) (cons 'nconc (reverse! (cons (bq-process2 p d) q))))))))) #| tests > ``(,a ,,a ,b ,@b ,,@b) `(,a ,1 ,b ,@b (unquote 2 3)) > `(,a ,1 ,b ,@b (unquote 2 3)) (1 1 (2 3) 2 3 2 3) (define a 1) (bq-process2 '`(,a (unquote unquote a)) 0) (define b '(unquote a)) (define unquote 88) (bq-process2 '``(,a ,,,@b) 0) ; etc. => (1 88 1) (define b '(a a)) (bq-process2 '``(,a ,,,@b) 0) ; etc. => (1 1 1) |# ;; minimal version with no optimizations, vectors, or dotted lists (define (bq-process0 x d) (define (bq-bracket x) (cond ((and (pair? x) (eq? (car x) 'unquote)) (if (= d 0) (cons list (cdr x)) (list list (list cons ''unquote (bq-process0 (cdr x) (- d 1)))))) ((and (pair? x) (eq? (car x) 'unquote-splicing)) (if (= d 0) (list 'copy-list (cadr x)) (list list (list list ''unquote-splicing (bq-process0 (cadr x) (- d 1)))))) (else (list list (bq-process0 x d))))) (cond ((symbol? x) (list 'quote x)) ((atom? x) x) ((eq? (car x) 'quasiquote) (list list ''quasiquote (bq-process0 (cadr x) (+ d 1)))) ((eq? (car x) 'unquote) (if (and (= d 0) (length= x 2)) (cadr x) (list cons ''unquote (bq-process0 (cdr x) (- d 1))))) (else (cons 'nconc (map bq-bracket x))))) #t